Develop Reference

Way to close TCP Connection and Exit Application

This is a TCP Program which receives data from a TCP connection, then parse it and transfer it to another TCP connection. When I exit application, it doesn't work. It will remain as a process in the system.
As I am not a very experienced developer, can someone please help me to find the error in this code..
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
using System.IO;
using System.Threading;
namespace Machine_Feeder
{
public partial class FeederControlMonitor : Form
{
TcpListener Listener = null;
public string Status = string.Empty;
public Thread T = null;
public FeederControlMonitor()
{
InitializeComponent();
}
private void FeederControlMonitor_Load(object sender, EventArgs e)
{
txtStatus.Text = "Feeder waiting for data...";
ThreadStart Ts = new ThreadStart(StartReceiving);
T = new Thread(Ts);
T.Start();
}
public void StartReceiving()
{
ReceiveTCP(9100);
}
public void ReceiveTCP(int portN)
{
try
{
Listener = new TcpListener(IPAddress.Any, portN);
Listener.Start();
}
catch (Exception ex)
{
File.WriteAllText(#"C:\\Drive\\ex.txt", ex.Message);
Console.WriteLine(ex.Message);
}
try
{
while (true)
{
Socket client = Listener.AcceptSocket();
var childSocketThread = new Thread(() =>
{
byte[] data = new byte[10000];
int size = client.Receive(data);
ParseData(System.Text.Encoding.Default.GetString(data));
client.Close();
});
childSocketThread.Start();
}
Listener.Stop();
}
catch (Exception ex)
{
File.WriteAllText(#"C:\\Drive\\ex.txt", ex.Message);
}
}
public void ParseData(string data)
{
var useFulData = data.Substring(data.IndexOf("F1")).Replace(" ", " ");// Space
useFulData = useFulData.Remove(useFulData.IndexOf("<ETX>"));
string[] delimeters = { "<DEL>", "<ESC>" };
var listOfValues = useFulData.Split(delimeters, StringSplitOptions.None).ToList();
int pos = 0;
for (int i = 1; i < listOfValues.Count; i += 2, pos++)
{
listOfValues[pos] = listOfValues[i];
}
listOfValues.RemoveRange(pos, listOfValues.Count - pos);
txtHealthCard.Invoke((Action)delegate { txtHealthCard.Text = listOfValues[0]; });
txtCID.Invoke((Action)delegate { txtCID.Text = listOfValues[1]; });
txtMedicalFitLocation.Invoke((Action)delegate { txtMedicalFitLocation.Text = listOfValues[2]; });
txtGender.Invoke((Action)delegate { txtGender.Text = listOfValues[3]; });
txtAge.Invoke((Action)delegate { txtAge.Text = listOfValues[4]; });
txtPatientName.Invoke((Action)delegate { txtPatientName.Text = listOfValues[5]; });
MyProtocolMaker(listOfValues[5],
listOfValues[4],
listOfValues[2],
listOfValues[3],
listOfValues[8],
listOfValues[1],
listOfValues[10],
);
}
private void btnExit_Click(object sender, EventArgs e)
{
Listener.Stop();
T.Abort();
this.Close();
}
private void MyProtocolMaker(
string patientName,
string patientAge,
string mfitLocation,
string gender,
string healthCardNo,
)
{
string feederInfo = "^^^P^PI" + healthCardNo + "^PN" + patientName + "^PA" + patientAge + "^PS" + gender + "^P7" + mfitLocation +"^_SS^^^_S";
System.Net.Sockets.TcpClient clientSocket = new System.Net.Sockets.TcpClient("127.0.0.1", 8001);
NetworkStream serverStream = clientSocket.GetStream();
byte[] outStream = System.Text.Encoding.ASCII.GetBytes(feederInfo);
serverStream.Write(outStream, 0, outStream.Length);
serverStream.Flush();
serverStream.Close();
clientSocket.Close();
}
private void FeederControlMonitor_FormClosing(object sender, FormClosingEventArgs e)
{
Listener.Stop();
T.Abort();
this.Close();
}
}
}

You problem is, that you are creating threads within the thread. These threads are keeping the application alive. Try marking them as background threads: (This is red-tape solution)
var childSocketThread = new Thread(() =>
{
byte[] data = new byte[10000];
int size = client.Receive(data); // <-- the thread hangs on these and will block termination
ParseData(System.Text.Encoding.Default.GetString(data));
client.Close();
});
childSocketThread.IsBackground = true; // <---
childSocketThread.Start();
When thread are not marked as background (default), they will block application termination. You should create a list to store the client threads, so you can exit those threads nicely.
You should never abort a thread, unless there is no other way. Instead of aborting, you should exit the while loop in the thread.
As nice way is using a ManualResetEvent:
fields:
private ManualResetEvent _terminating = new ManualResetEvent(false);
in thread:
while (_terminating.WaitOne(0))
{
// thread code
}
on exit:
_terminating.Set();
T.Join();
Sidenote: TCP is streaming, so just reading 10k of bytes ones, does not guarantee a complete packet.

C# handler not creating and failing when using .CreateHandler()

I'm creating a game in which I use TCP/IP connection. The problem is that I'm using .Invoke to help me receive and send message.
The program goes like this: I'm my first window, i'm starting and connecting to the server like this :
{
TcpListener listener = new TcpListener(IPAddress.Any, this.port);
listener.Start();
try {
this.client = listener.AcceptTcpClient();
gameWindow = new GameWindow(this.client, true);
gameWindow.StartGame();
}
}
then i'm connecting to it like this:
{
IPEndPoint ipEnd = new IPEndPoint(this.serverIP, this.port);
{
try {
client.Connect(ipEnd);
if (client.Connected) {
gameWindow = new GameWindow(this.client, false);
gameWindow.StartGame();
}
}
}
The constructor for gameWindow (which is a form) looks like this:
public GameWindow(TcpClient thisClient, bool isServer)
{
InitializeComponent();
this.client = thisClient;
this.reader = new StreamReader(thisClient.GetStream());
this.writer = new StreamWriter(thisClient.GetStream());
this.writer.AutoFlush = true;
}
I must wait for the server to send a message to the client, and then start the client ( I have a function .startGame() that uses .ShowDialog() and creates some pictureBoxs)
But nowhere I can get my handle created. I've tried to put this.createHandle() (read about it here) into GameWindow_Load but still not works. If I try to send a message with:
workerSendData.RunWorkerAsync(); I get:
Additional information: Invoke or BeginInvoke cannot be called on a control until the window handle has been created.
What can I do to get my handler created? Using Thread.Sleep will sleep my whole UI, which does not work (a "solution" found on the internet)
My code for sending message :
private void workerSendData_DoWork(object sender, DoWorkEventArgs e)
{
if (client.Connected) {
this.writer.WriteLine(this.toSend); // aici trimitem datele.
// de modificat : aici vom adauga in lista noastra miscarile.
this.Invoke(new MethodInvoker(delegate () { MessageBox.Show("Me:" + this.toSend + "\n"); }));
}
else {
MessageBox.Show("Send failed");
}
workerSendData.CancelAsync();
}
My code for receiving data:
private void workerReceiveData_DoWork(object sender, DoWorkEventArgs e)
{
while (client.Connected) {
try {
this.received = this.reader.ReadLine();
this.myTurn = true;
this.Invoke(new MethodInvoker(delegate () {
MessageBox.Show("This has been received: " + this.received);
/*this.tbReceive.AppendText("You:" + this.received + "\n");*/
}));
this.received = "";
}
catch (Exception x) {
MessageBox.Show(x.Message.ToString());
}
}
}

It seems that you cannot invoke an action before the Window is fully initialized and loaded. Assuming you are working in Windows Forms, there is a solution provided by #Greg D on this question, but it doesn't be to be the safest way to go.
I would suggest that you try to find a way to start the worker only after the window is loaded (for example using the Loaded event), so that the handle is definitely ready and this situation does not occur.

Writing text to a textbox's text property in a WINFORM

New to WinForms but not ASP.NET or C#. Trying to make client/server app. Successfully received data from client on server but having troubles displaying it on server program winform. Codes are:
Server App code:
using System;
using System.Windows.Forms;
using System.Net.Sockets;
using System.Net;
namespace Server_App
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
IPEndPoint ep = new IPEndPoint(IPAddress.Loopback, 1234); //configure host
TcpListenerEx listener = new TcpListenerEx(ep); //set host to listen
if (!listener.Active)
{
listener.Start();
}
while (true)
{
const int byteSize = 1024 * 1024;
byte[] message = new byte[byteSize];
var s = listener.AcceptTcpClient();
s.GetStream().Read(message, 0, byteSize); //obtaining network stream and receiving data through .Read()
message = cleanMessage(message);
string g = System.Text.Encoding.UTF8.GetString(message);
addMessage(g);
}
}
private void addMessage(string m)
{
this.textBox1.Text = textBox1.Text + Environment.NewLine + " >> " + m;
}
private byte[] cleanMessage(byte[] rawMessageByte)
{
byte[] cleanMessage = rawMessageByte.Where(b => b != 0).ToArray();
return cleanMessage;
}
}
}
Client App code:
using System;
using System.Net.Sockets;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace ClientApp
{
public partial class ClientApp : Form
{
public ClientApp()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
var message = System.Text.Encoding.UTF8.GetBytes(txtFromClient.Text);
using (var client = new TcpClient("127.0.0.1", 1234))//make connection with the host
{
NetworkStream stream = client.GetStream();/*obtain network stream*/
stream.Write(message, 0, message.Length);
}
}
private void textBox1_Click(object sender, EventArgs e)
{
txtFromClient.Text = "";
}
}
}
Everything is happening as planned except for displaying received data on server program's Form1's textbox. On debugging, I confirmed the correct value received in variable m of line this.textBox1.Text = textBox1.Text + Environment.NewLine + " >> " + m;. Only problem is that this value cannot be displayed and hence seen on the Form1 of server program.

With the help and guidance from #AdrianoRepetti, solution to the given problem was furnished through the following code:
using System;
using System.Windows.Forms;
using System.Net.Sockets;
using System.Net;
using System.Linq;
namespace Server_App
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
backgroundWorker1.WorkerReportsProgress = true;
}
private void button1_Click(object sender, EventArgs e)
{
IPEndPoint ep = new IPEndPoint(IPAddress.Loopback, 1234); //configure host
if(!backgroundWorker1.IsBusy)
{
backgroundWorker1.RunWorkerAsync(ep); //called to start a process on the worker thread and send argument (listener) to our workerprocess.
}
}
private void backgroundWorker1_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
IPEndPoint ep = e.Argument as IPEndPoint;
TcpListenerEx listener = new TcpListenerEx(ep);
if (!listener.Active)
{
listener.Start();
}
while (true)
{
try
{
const int byteSize = 1024 * 1024;
byte[] message = new byte[byteSize];
using (var s = listener.AcceptTcpClient())
{
s.GetStream().Read(message, 0, byteSize);//obtaining network stream and receiving data through .Read()
message = cleanMessage(message);
string g = System.Text.Encoding.UTF8.GetString(message);
backgroundWorker1.ReportProgress(0, g);
}
}
catch (Exception ex)
{
backgroundWorker1.ReportProgress(0, ex.Message);
}
finally
{
listener.Stop();
}
}
}
private void backgroundWorker1_ProgressChanged(object sender, System.ComponentModel.ProgressChangedEventArgs e)
{
textBox1.AppendText(Environment.NewLine + ">> " + e.UserState);
}
private byte[] cleanMessage(byte[] rawMessageByte)
{
byte[] cleanMessage = rawMessageByte.Where(b => b != 0).ToArray();
return cleanMessage;
}
}
}
Hope it helps.

Cross thread operation on the server code

I am new in server client programming so i wrote this server code
namespace TCP_SERVER
{
public partial class Form1 : Form
{
private ArrayList nSockets;
public Form1()
{
InitializeComponent();
}
public void listenerThread()
{
new TcpListener(IPAddress.Any, 8080);
TcpListener tcpListener = new TcpListener(8080);
tcpListener.Start();
while (true)
{
Socket handlerSocket = tcpListener.AcceptSocket();
if (handlerSocket.Connected)
//try
//{
{
lbConnections.Items.Add(handlerSocket.RemoteEndPoint.ToString() + " connected.");
lock (this)
{
nSockets.Add(handlerSocket);
}
ThreadStart thdstHandler = new
ThreadStart(handlerThread);
Thread thdHandler = new Thread(thdstHandler);
thdHandler.Start();
}
//}
//catch (Exception ex)
//{
// MessageBox.Show(ex.Message);
//}
}
}
public void handlerThread()
{
Socket handlerSocket = (Socket)nSockets[nSockets.Count-1];
NetworkStream networkStream = new
NetworkStream(handlerSocket);
int thisRead=0;
int blockSize=1024;
Byte[] dataByte = new Byte[blockSize];
lock(this)
{
// Only one process can access
// the same file at any given time
Stream fileStream = File.OpenWrite(#"C:\Users\KINENE\Documents\submitted.txt");
while(true)
{
thisRead=networkStream.Read(dataByte,0,blockSize);
fileStream.Write(dataByte,0,thisRead);
if (thisRead==0) break;
}
fileStream.Close();
}
lbConnections.Items.Add("File Written");
handlerSocket = null;
}
private void Form1_Load(object sender, EventArgs e)
{
IPHostEntry IPHost = Dns.GetHostByName(Dns.GetHostName());
lblStatus.Text = "My IP address is " + IPHost.AddressList[0].ToString();
nSockets = new ArrayList();
Thread thdListener = new Thread(new ThreadStart(listenerThread));
thdListener.Start();
}
}
}
i get the error on this line of code
lbConnections.Items.Add(handlerSocket.RemoteEndPoint.ToString() + " connected.");
lock (this)

You are accessing UI elements from another thread, which is not allowed.
You should call Invoke to call the code on the right thread:
this.Invoke((MethodInvoker)delegate()
{
lbConnections.Items.Add(handlerSocket.RemoteEndPoint.ToString() + " connected.");
});

Winforms, Invokes and a problematic button

I am trying to build a chat, basically i used the invoke function what a thread.
I am able to read what the server sends me, but i am able to write only once. i am trying to finish this but not sure how to write to server each time the server:
(take into account that i wrote this before in console application form and the server works fine... i.e. the problem isnt with the server).
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
Button btn1 = new Button();
btn1.Click += button1_Click;
}
StreamReader sr;
StreamWriter sw;
TcpClient connection;
private void Form1_Load(object sender, EventArgs e)
{
connection = new TcpClient("127.0.0.1", 5000);
sr = new StreamReader(connection.GetStream());
sw = new StreamWriter(connection.GetStream());
}
private void button2_Click(object sender, EventArgs e)
{
Thread t2 = new Thread(Reader);
t2.Start(connection);
}
string msg;
public void Reader(object o)
{
TcpClient con = o as TcpClient;
if (con == null)
return;
while (true)
{
msg = sr.ReadLine();
Invoke(new Action(Output));
}
}
public void Output()
{
ChatScreen.Text = msg;//set the message on the screen
}
string textinput;
private void button1_Click(object sender, EventArgs e)
{
textinput = InputLine.Text;
sw.WriteLine(textinput);// this thing, writes once, multiple clicks wont send a new line to the server :(..the problem is in this button
sw.Flush();
}
}
what I thought to do is to connect the button so it will be able to do multiple clicks ..e.g btn.Click()..or run a thread with invoke on the WriteLine (but my intuition says that making the button click several times would make the program work

You need to stop the thread process when you close the form, if not when you try to do the invoke, it will fail because the form is disposed and it can't be used to do an invoke. You can override the dispose method to stop the reader thread or you can do it on the onclose method. Or you can check on the reader process if the control it's available (it is not disposed) and if it's not available finish the read process.
You should prevent that the reader process will be launch multiple times too, to prevent errors, so you need to disable the button when the thread is run.
Edited:
You can use something like the following code to read multiple lines and to stop the thread when you close the form.
private bool mbIsRunning = true;
private void Form1_Closing(object sender, System.ComponentModel.CancelEventArgs e)
{
lock (this)
{
mbIsRunning= false;
}
}
private bool IsRunning
{
get
{
lock(this)
{
return mbIsRunning;
}
}
}
string msg;
public void Reader(object o)
{
TcpClient con = o as TcpClient;
if (con == null)
return;
while (IsRunning)
{
msg = reader.ReadLine();
string line;
while( (line = reader.ReadLine()) != null )
{
msg = msg + Enviroment.NewLine + line;
}
Invoke(new Action(Output));
}
}

Running up your code, I get a bunch of errors - from the TcpClient throwing an exception and so on.
However, assuming that you haven't posted all of your code, I would recommend putting a try...catch around all of your functions, and then breakpoints in the catch to see what the problem is. Examine the exceptions - exceptions should only be thrown in exceptional circumstances - so your code should really work without doing that.

I do concat on my server code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.IO;
using System.Threading;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
TcpListener server = new TcpListener(IPAddress.Any, 5000);
server.Start();
Console.WriteLine("Server started");
string word = "";
savedObject saved = new savedObject();
while (true)
{
TcpClient connection = server.AcceptTcpClient();
Console.WriteLine("connection accepted");
ThreadPool.QueueUserWorkItem(saved.ProssecClient, connection);
}
}
}
}
class savedObject
{
Dictionary<string, StreamWriter> dic = new Dictionary<string, StreamWriter>();
StreamReader[] sr1 = new StreamReader[100];
StreamWriter[] sw1 = new StreamWriter[100];
string[] name = new string[100];
int m;
int a;
int g;
string word;
public string AllWords(string sit)
{
word += sit + " ";// here i concat them
return word;
}
public string word2()
{
return word;
}
public void ProssecClient(object o)
{
TcpClient connection = o as TcpClient;
if (connection == null)
{
return;
}
StreamReader sr = new StreamReader(connection.GetStream());
StreamWriter sw = new StreamWriter(connection.GetStream());
sr1[a++] = new StreamReader(connection.GetStream());
sw1[m++] = new StreamWriter(connection.GetStream());
string word2 = "";
sw.WriteLine("Please, fill your name: ");
name[g++] = sr.ReadLine();
if (name[g] != null && sw1[m] != null)
{
dic.Add(name[g], sw1[m]);
}
try
{
while (true)
{
int i = 0;
word2 = AllWords(sr.ReadLine());
for (i = 0; i < 3; i++)
{
if (sw1[i] != null)
{
sw1[i].WriteLine( name[i] + ": " + word2);// here is the words that are sent..
sw1[i].Flush();
}
}
}
}
catch { Console.WriteLine("client left"); }
}
}